The present invention relates to a mobile communications system and a controller, and to a control method used therein.
In a cellular mobile communications system, a mobile station for performing a communication including voice communication performs handover when moving between wireless zones (cells) corresponding to wireless base stations. During the handover procedure, the mobile station transmits radio signals to the plurality of wireless base stations involved in the handover. The wireless base stations involved in the handover transmit a user signal included in the radio signal received from the mobile station to a wireless base station controller, and the wireless base station controller combines the received user signal and transmits it to a core network via a mobile communication switching center.
The wireless base station controller receives the signal from the core network via the mobile communication switching center, and transmits the received signal to the plurality of wireless base stations involved in the handover. The wireless base stations involved in the handover transmit the signal received from the wireless base station controller to the mobile station, which combines the signal received from the wireless base stations involved in the handover.
Meanwhile, in cellular mobile communication systems, the adoption of a high-speed data communication methods specializing in data communication has been under research and development. For example, HSDPA (High Speed Downlink Packet Access) technologies on the W-CDMA (Wide band Code Division Multiple Access) mobile communication system, and EV-DO (Evolved High-speed Data Only) technologies on the CDMA 2000 system etc. correspond to the above high-speed data communication method. For example, 3Gpp TS 25.308 V5.3.0 etc. specifies HSDPA, and 3GPP2 S.R0023 version 2.0 etc. specifies EV-DO.
In Published Unexamined Japanese Patent Application No. 2001-217770, an outer loop transmit power control method for mobile stations during handover in a mobile communication system is disclosed. In this method, where the mobile station is communicating with the only one wireless base station, the wireless base station controls the transmit power of the mobile station based on the quality of the signal received from the mobile station. When the mobile station performs a handover, the control station combines the reception quality in the plurality of wireless base stations involved in the handover. The wireless base station controller controls the transmit power of the mobile station based on the combined reception quality.
Even where the communication including voice communication and the high-speed data communication are performed at the same time, a quality of the cellular mobile communication is improved by performing outer loop control. However, until now, favorable results have not been achieved.